From: Michal Hocko <mhocko@suse.cz>
To: Li Zefan <lizefan@huawei.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Tejun Heo <tj@kernel.org>, Glauber Costa <glommer@parallels.com>,
KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>,
Johannes Weiner <hannes@cmpxchg.org>,
LKML <linux-kernel@vger.kernel.org>,
Cgroups <cgroups@vger.kernel.org>,
linux-mm@kvack.org
Subject: Re: [PATCH 13/12] memcg: don't need memcg->memcg_name
Date: Mon, 8 Apr 2013 16:25:03 +0200 [thread overview]
Message-ID: <20130408142503.GH17178@dhcp22.suse.cz> (raw)
In-Reply-To: <51626584.7050405@huawei.com>
On Mon 08-04-13 14:36:52, Li Zefan wrote:
[...]
> @@ -5188,12 +5154,28 @@ static int mem_cgroup_dangling_read(struct cgroup *cont, struct cftype *cft,
> struct seq_file *m)
> {
> struct mem_cgroup *memcg;
> + char *memcg_name;
> + int ret;
The interface is only for debugging, all right, but that doesn't mean we
should allocate a buffer for each read. Why cannot we simply use
cgroup_path for seq_printf directly? Can we still race with the group
rename?
> +
> + /*
> + * cgroup.c will do page-sized allocations most of the time,
> + * so we'll just follow the pattern. Also, __get_free_pages
> + * is a better interface than kmalloc for us here, because
> + * we'd like this memory to be always billed to the root cgroup,
> + * not to the process removing the memcg. While kmalloc would
> + * require us to wrap it into memcg_stop/resume_kmem_account,
> + * with __get_free_pages we just don't pass the memcg flag.
> + */
> + memcg_name = (char *)__get_free_pages(GFP_KERNEL, 0);
> + if (!memcg_name)
> + return -ENOMEM;
>
> mutex_lock(&dangling_memcgs_mutex);
>
> list_for_each_entry(memcg, &dangling_memcgs, dead) {
> - if (memcg->memcg_name)
> - seq_printf(m, "%s:\n", memcg->memcg_name);
> + ret = cgroup_path(memcg->css.cgroup, memcg_name, PAGE_SIZE);
> + if (!ret)
> + seq_printf(m, "%s:\n", memcg_name);
> else
> seq_printf(m, "%p (name lost):\n", memcg);
>
> @@ -5203,6 +5185,7 @@ static int mem_cgroup_dangling_read(struct cgroup *cont, struct cftype *cft,
> }
>
> mutex_unlock(&dangling_memcgs_mutex);
> + free_pages((unsigned long)memcg_name, 0);
> return 0;
> }
> #endif
> --
> 1.8.0.2
> --
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--
Michal Hocko
SUSE Labs
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next prev parent reply other threads:[~2013-04-08 14:25 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-04-08 6:32 [PATCH 0/12][V2] memcg: make memcg's life cycle the same as cgroup Li Zefan
2013-04-08 6:33 ` [PATCH 01/12] memcg: take reference before releasing rcu_read_lock Li Zefan
2013-04-08 6:33 ` [PATCH 02/12] memcg: avoid accessing memcg after releasing reference Li Zefan
2013-04-08 6:33 ` [PATCH 03/12] Revert "memcg: avoid dangling reference count in creation failure." Li Zefan
2013-04-09 2:50 ` Kamezawa Hiroyuki
2013-04-08 6:33 ` [PATCH 04/12] memcg, kmem: fix reference count handling on the error path Li Zefan
2013-04-09 2:51 ` Kamezawa Hiroyuki
2013-04-08 6:34 ` [PATCH 05/12] memcg: use css_get() in sock_update_memcg() Li Zefan
2013-04-08 6:34 ` [PATCH 06/12] memcg: don't use mem_cgroup_get() when creating a kmemcg cache Li Zefan
2013-04-09 2:53 ` Kamezawa Hiroyuki
2013-04-08 6:34 ` [PATCH 07/12] memcg: use css_get/put when charging/uncharging kmem Li Zefan
2013-04-08 14:14 ` Michal Hocko
2013-04-09 2:55 ` Kamezawa Hiroyuki
2013-04-08 6:34 ` [PATCH 08/12] memcg: use css_get/put for swap memcg Li Zefan
2013-04-08 6:35 ` [PATCH 09/12] cgroup: make sure parent won't be destroyed before its children Li Zefan
2013-04-08 15:36 ` Tejun Heo
2013-04-08 6:35 ` [PATCH 10/12] memcg: don't need to get a reference to the parent Li Zefan
2013-04-08 6:36 ` [PATCH 11/12] memcg: kill memcg refcnt Li Zefan
2013-04-08 6:36 ` [PATCH 12/12] memcg: don't need to free memcg via RCU or workqueue Li Zefan
2013-04-08 14:15 ` Michal Hocko
2013-04-09 2:57 ` Kamezawa Hiroyuki
2013-04-08 6:36 ` [PATCH 13/12] memcg: don't need memcg->memcg_name Li Zefan
2013-04-08 14:25 ` Michal Hocko [this message]
2013-04-09 1:28 ` Li Zefan
2013-04-09 3:10 ` Kamezawa Hiroyuki
2013-04-09 3:18 ` Li Zefan
2013-04-09 3:46 ` Kamezawa Hiroyuki
2013-04-09 7:55 ` Glauber Costa
2013-04-09 3:59 ` Tejun Heo
2013-04-09 7:53 ` Glauber Costa
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